1. Field of the Invention
The present invention relates to an enhanced peanut plant line and the products derived therefrom.
2. Discussion of the Prior Art
The cultivated peanut (Arachis hypogaea L.) is a self-pollinating annual herbaceous legume characterized by seeds with high oil (45-55%) and protein (25-35%) and a low percentage of carbohydrates and ash. The quality of edible peanuts is due principally to the chemical composition of the oil, protein and carbohydrate fractions of the seeds.
The cultivated peanut originated in South America, along the eastern slopes of the Andes mountains. It now is widely grown and well adapted to tropical, sub-tropical and warm temperate areas of the world. It currently ranks ninth in area among the row crops in the United States and second in dollar value per acre. In the United States, peanuts are utilized primarily as whole seeds and for making peanut butter, while elsewhere in the world they are mainly crushed for oil. Approximately 70% of the world's peanuts are crushed to provide about 20% of the world's vegetable oil. Seeds of the commonly grown cultivars contain 40-52% oil and 25-32% protein.
Since 1928, dramatic improvements have been made in the peanut plant. In the early days of programs, breeders had as their goal the development of a variety that is the best market type and/or also well suited to "hogging off." Today the program must meet the needs of three groups of people: (1) the growers who want a higher yielding variety with more resistance to pests and environmental stresses; (2) the processors who desire more uniform maturity and more favorable processing traits; and (3) the consumer who desires improved nutritional properties, as well as fruit and seeds with preferred shape, size, color, texture and flavor.
Programs have been successful in redesigning the peanut to meet most o these changing needs. The peanut of 40 years ago (Dixie Runner) partitioned only 41% of its assimilate to fruits, while Early Bunch, released in 1977, is an extremely efficient producer of peanuts, partitioning 98% of its assimilate to the fruit. The success of these programs can also be seen in the distribution of varieties, which accounts for approximately 90% of the peanuts produced in the United States. The Florunner variety alone accounted for 71% of the United States peanut acreage in 1982.
Peanut improvement projects generally involve controlled hybridizations followed by pedigreed selection within and between thousands of different lines. The procedure, which spans a period of 10-20 years, is to discard all undesirable plants and lines and to save only those with apparent superiority in economically desirable characteristics. A prerequisite to success is a source of genetic variability and the means of transferring it into the desired variety.
Fortunately, there is a considerable amount of variability available in the cultivated species, especially in morphological and chemical characteristics. The oil content of different genotypes varies from less than 45% to over 55%, and the fatty acid composition of the oil of different lines also shows considerable variability. Some peanut lines have polyunsaturated to saturated oil ratios of almost 2:1, the ratio considered desirable for reduction of blood serum cholesterol. Genetic variability is also available within the species to increase some deficient amino acids, especially methionine, but more variation is needed. More resistance to certain diseases, nematodes, toxin-producing molds and drought is also required.
In some of the wild Arachis species, there is near immunity to rust and Cercospora leafspot disease, as well as spider mite resistance, resistance to lesser cornstalk borer and many other valuable features. However, the wild diploid species (2N=20) are not sexually compatible with the cultivated species where 2N=40. Techniques of embryo rescue, where newly produced embryos are surgically removed and grown in tissue culture and protoplast fusion, which combines cells from different species and attempts to produce whole plants from these vegetative hybrids, may open a vast new gene pool which has, until now, been largely unaccessible to the peanut breeder.
The improvement of peanut oil quality has long been an objective of the successful breeding program since it influences the shelf-life and nutritional quality of manufactured products Norden, Sunshine State April Res. Report, January, 1968, pages 14-16; and Norden et al, Oleagineaux, Vol. 23, pages 583-585!. Since fatty acids make up the major portion of the weight of an oil molecule, the physical and chemical properties of the oil tend to be determined by the properties of the fatty acids which predominate in their makeup. Although as may as twelve fatty acids have been reported in peanuts, only three are present in amounts exceeding 5%: palmitic, oleic and linoleic Ahmed et al, Peanut Science and Technology, pages 655-688, Pattee and Young (ed.) (1982)!. These three acids comprise about 90% of the fatty acid composition of the oil, with oleic and linoleic oils comprising about 80%. The remainder of the fatty acids comprise about 10%, each ranging in concentration from 0.02% to 3.59%.
Peanut genotypes are known with as low as 35% and as high as 71% oleic acid and with linoleic acid contents ranging from as low as 11% to as high as 43% Bovi, Ph.D. Dissertation, University of Florida, page 119 (1982); Treadwell et al, Oleagineaux, Vol. 38, pages 381-385 (1983); Worthington et al, Oleagineaux, Vol. 26, pages 695-700 (1971); Worthington et al, J. Amer. Oil Chem. Soc., Vol. 54, pages 105-108 (1977)!. Studies by Worthington et al (1977), supra, showed that stability of peanut oil and peanut butter samples were highly correlated with levels of linoleic acid, and they concluded that selection for lower levels of linoleic acid in the development of new varieties of peanuts should result in products with significantly improved shelf life.
"Florunner," which is currently the most widely grown commercial peanut cultivar in the United States, has approximately 51% oleic acid and 29% linoleic acid, which results in an oleic acid/linoleic acid (O/L) ratio of slightly less than 2:1.
These two fatty acids dictate the final quality of the peanut product. Oleic acid has one double bond and linoleic acid has two double bonds. The large quantity of linoleic acid partly determines the shelf life of peanuts, i.e, that length of time a peanut product may be stored before becoming rancid. The fewer double bonds present in the oil, the longer the shelf life.
"Sunrunner," another commercially popular market type cultivar, also has a relatively high content of linoleic acid.
Health considerations have made oils with more double bonds (higher unsaturation levels) more desirable as a factor in the reduction of atherosclerosis. Thus, the breeder is faced with the paradox of breeding for more unsaturation for the consumer and less unsaturation for the processor. Recent research in human nutrition has indicated that the high levels of the mono-unsaturated oleic acid is as effective as the polyunsaturated linoleic acid in lowering the blood plasma cholesterol Mattson et al, J. Lipid Research, Vol. 26, pages 194-202 (1985)!. If peanut lines with higher oleic acid and lower linoleic acid could be developed, such lines would be desired by both the consumer and the processor.
In the parent applications identified above, the entire contents and disclosures of which are incorporated herein by reference, there is described a novel peanut line from which can be derived a novel peanut seed which yields peanut products, in particular oil and food products, having enhanced shelf lives and nutritional qualities because of the high oleic acid and low linoleic acid contents and iodine values thereof. The novel germ-plasm is true-breeding and may also be hybridized with other peanut stocks to produce novel peanut hybrids through selection.
It is an object of the present invention to provide a new peanut plant line for producing peanut seeds which have an unusually high oleic acid content and low linoleic acid level, as well as breeding lines that have substantially the same yield and market grade as existing runner market type cultivars.
It is another object of the present invention to provide a novel peanut product having an enhanced shelf life and high oleic acid content and low linoleic acid level.